API

​

Evaluate

PEX.evaluatePresentation(presentationDefinition, verifiablePresentation);
PEXv1.evaluatePresentation(presentationDefinition, verifiablePresentation);
PEXv2.evaluatePresentation(presentationDefinition, verifiablePresentation);

Description

These three methods are quite similar. The first One receives a presentation definition object, decides the version based upon feature detection and acts accordingly. The other two are specific to their Presentation Exchange definition version.

For more detailed difference between v1 and v2 please read the From V1 to V2 section.

Evaluates whether a presentation submission meets the requested presentation definition Since this method will be used both before and after creating a VerifiablePresentation, we accept both signed and unsigned version of a presentation here.

​

Parameters

​

Return value

If evaluation is successful, value will be a non-null PresentationSubmission mapping the submitted credentials to the requested inputs.

interface EvaluationResults {
  value?: PresentationSubmission;
  warnings?: string[];
  errors?: Error[];
  verifiableCredential: (IVerifiableCredential | JwtWrappedVerifiableCredential | string)[];
}

​

SelectFrom

PEX.selectFrom(presentationDefinition, credentials, { holderDIDs });
PEXv1.selectFrom(presentationDefinitionV1, credentials, { holderDIDs });
PEXv2.selectFrom(presentationDefinitionV2, credentials, { holderDIDs });

Description

These three methods are quite similar. The first One receives a presentation definition object, decides the version based upon feature detection and acts accordingly. The other two are specific to their version.

For more detailed difference between v1 and v2 of the spec please read the From V1 to V2 section.

Gathers the matching credentials that fit a given presentation definition. Please note that there could be multiple results fitting the same criteria. This basically only filters out the credentials that do not match the definition. You, or rather the user, typically has to do a final selection.

​

selectFrom Parameters

​

Return value

• If the selection was successful or partially successful, the matches array will consist of SubmissionRequirementMatch object(s), representing the matching credentials for each SubmissionRequirement in the presentationDefinition input parameter.
• If the selection was not successful, the errors array will consist of Checked object(s), representing what has failed in your selection process.

import { Status } from './ConstraintUtils';

interface SelectResults {
  errors?: Checked[];
  matches?: SubmissionRequirementMatch[];
  /**
   * This is the parameter that the PEX library user should look into to determine what to do next
   * Status can have three values:
   *  1. INFO: everything is fine, you can call `presentationFrom` after this method
   *  2. WARN: method was called with more credentials than required.
   *       To enhance credential holderDID's privacy it is recommended to select credentials which are absolutely required.
   *  3. Error: the credentials you've sent didn't satisfy the requirement defined presentationDefinition object. Do not submit!
   */
  areRequiredCredentialsPresent: Status;
  /**
   * All matched/selectable credentials
   */
  verifiableCredential?: (IVerifiableCredential | JwtWrappedVerifiableCredential | string)[];
  /**
   * Following are indexes of the verifiableCredentials passed to the selectFrom method that have been selected.
   */
  vcIndexes?: number[];
  warnings?: Checked[];
}

interface SubmissionRequirementMatch {
  name?: string;
  rule: Rules;
  min?: number;
  count?: number;
  max?: number;
  vc_path: string[];
  from?: string[];
  from_nested?: SubmissionRequirementMatch[]; // VerifiableCredential Address
}

​

PresentationFrom

PEX.presentationFrom(presentationDefinition, selectedCredentials, { holderDID });
PEXv1.presentationFrom(presentationDefinitionV1, selectedCredentials, { holderDID });
PEXv2.presentationFrom(presentationDefinitionV2, selectedCredentials, { holderDID });

Description

These three methods are quite similar. The first One receives a presentation definition object, decides the version based upon feature detection and acts accordingly. The other two are specific to their version.

**For more detailed difference between v1 and v2 specification please read the From V1 to V2 section **.

Creates the corresponding Presentation Submission object to be included in the Verifiable Presentation response, which maps the submitted credentials to the requested inputs in the presentationDefinition input parameter.

​

presentationFromV1 Parameters

​

presentationFromV2 Parameters

​

Return value

If the selected credentials successfully match the submission requirements in the presentation definition, the return value will be a non-null ‘Presentation’ containing a PresentationSubmission

interface PresentationSubmission {
  id?: string;
  definition_id: string;
  descriptor_map: Descriptor[];
}

​

Validation

PEX.validateDefinition(objToValidate);
PEXv1.validateDefinition(objToValidate);
PEXv2.validateDefinition(objToValidate);

validateSubmission(objToValidate);

​

Description

A validation utility function for PresentationDefinition and PresentationSubmission objects. If you know the version of your presentation definition you can call version-specific functions. If not you can call the general one (located in PEX) to first determine the version and then validate the presentation definition object against that version’s specific rules.

​

Parameters

​

Return value

The validate method returns a validated results array NonEmptyArray<Checked> , with structure:

interface Checked {
  tag: string;
  status: Status;
  message?: string;
}

status can have following values 'info' | 'warn' | 'error'

​

Definition Version Discovery

PEX.definitionVersionDiscovery(presentationDefinition);

​

Description

A utility function for PresentationDefinition objects. This method will determine the version of your presentationDefinition object.

​

Parameters

​

Return value

The definitionVersionDiscovery method returns a version or an error, with following structure:

interface DiscoveredVersion {
  version?: PEVersion;
  error?: string;
}

enum PEVersion {
  v1 = 'v1',
  v2 = 'v2',
}